1. Field of the Invention
The present invention relates to a reclining seat suited for use in an automotive vehicle and capable of appropriately adjusting the angle of inclination of a seat back relative to a seat cushion.
2. Description of Related Art
A conventional automobile reclining seat includes a sector gear fixed to a seat back and a worm gear rotatably mounted in a seat cushion so as to be engageable with the sector gear. The worm gear is connected to an operating shaft, and engagement of the worm gear with the sector gear is released by pulling the operating shaft in a direction axially thereof and subsequently lifting it. Under this condition, the angle of inclination of the seat back can be easily and rapidly changed by applying a load to the seat back. When the operator releases the operating shaft, the worm gear engages with the sector gear again to retain the angle of inclination of the seat back. In the case where fine adjustment of the angle of inclination of the seat back is required, rotation of the operating shaft causes rotation of the worm gear, which in turn causes a gradual rotation of the sector gear in engagement with the worm gear, making it possible to steplessly change the angle of inclination of the seat back to a desired one (see, for example, Japanese Utility-Model Publication (examined) No. 42-7950).
Another conventional automobile reclining seat includes a worm wheel fixed to a seat cushion and a worm gear rotatably mounted in a seat back with the worm wheel being in engagement with the worm gear. The worm gear has a groove defined therein to loosely receive a peripheral edge of the worm wheel. When the peripheral edge of the worm wheel is inserted into the groove of the worm gear by rotating a handle connected to the worm gear, engagement of the worm gear with the worm wheel is released, making it possible to change the angle of inclination of the seat back to a desired one. After the angle of inclination of the seat back has been changed, release of the handle causes a spring to rotate the worm gear by 90.degree., resulting in a locked condition in which the worm gear is again held in engagement with the worm wheel. If the handle together with the worm gear is rotated gradually, the worm wheel in engagement with the worm gear is also rotated gradually, enabling fine adjustment of the angle of inclination of the seat back (see, for example, Japanese Patent Publication (examined) No. 52-9892).
Furthermore, a reclining seat having a sector gear fixed to a seat back frame and a lock gear in engagement with the sector gear is known wherein the angle of inclination of the seat back can be appropriately changed by manually releasing engagement of the sector gear with the lock gear.
In each of the above-described conventional reclining seats, however, after mating parts such as the sector gear, the worm gear or the like have been incorporated into the seat back, the seat back must be covered with a cushioning material of at least about 35 millimeters thick to remove a sense of foreign substances, making it difficult to provide easy-to-make reclining seats.
Also, it is the general practice that when a relatively large impact is applied to the reclining seat due to, for example, a vehicle collision, impact energy is generally absorbed by deformation of the sector gear or the like. However, some of the conventional reclining seats cannot fully absorb such large impact energy.
Moreover, because a greater trochanter of a seat occupant is spaced a distance away from the center of rotation of the seat back, the hip of the seat occupant slides on the seat in inclining the seat back, thus giving the seat occupant an unpleasant feeling.